UNAVCO can assist with GNSS and other station reconnaissance as needed. The following issues are considered during GNSS site selection.

Sky View

A clear view of the sky with no obstructions above an
inclination angle of 10-15 degrees is ideal. A station obstruction diagram should be sketched or pictures taken to identify the approximate distance and bearing to the nearest obstacles.

Foliage

Tall, dense trees
and foliage near the site can contribute to intermittent signal loss,
just as buildings do. Be aware of the impact of seasonal foliage when
reconnaissance is conducted during the cold or dry season. If small trees are
present but do not block the sky appreciably, assess their rate of
growth if the station is to be occupied for several years.

Reflectors

Flat surfaces (vertical or horizontal) near the antenna can cause serious
multipath interference. As a rule of thumb, a one-story building should
be at least 50 feet away while taller buildings need to be farther away.

Other potential fixed reflectors include chain-link fences, metal
objects located in the vicinity, and time-varying reflectors such as
parked cars, moving vehicles, scaffolding, etc.

Radio Interference

Potential sources of radio interference include high-power television
or microwave transmission towers. Ideally, the site should be kept at least
1 km away from such structures.

Weather

Weather conditions are not normally a factor for permanent site
selection since automation is a primary goal and maintenance visits can
be arranged during periods of good weather. The local climate will
mainly dictate the choice of equipment installed at the site; for instance, in a cold climate, snow accumulation on the antenna may
become a factor, and an antenna radome should be considered.

Data Quality

During the initial visit to the proposed site, try to collect data
for at least 24 hours (preferably 48 hours) to assess the quality of
the site.

Communications

If
the data are to be telemetered, consider the requirements for your
chosen mode of communication. If using a cell modem, is there cell
service at the site? If using a radio modem, does the site have a
relatively uninterrupted view to the master radio? If telemetry is critical, test
out the communications equipment before committing to the site.

Site Access, Permissions, and Security

Consider ease of access and proper authorization from
property owners. For example, permission to build a station may
be granted by the owner, but access may have to be negotiated with
landowners whose properties are adjacent to the site in question. Names
and numbers of site contacts should be well documented.

Inquire with locals and/or police about vandalism incidents. There may be
additional cost involved if a fence or other perimeter enclosure has to
be built to protect the site, or if special precautions must be taken
to camouflage it. Site safety and security must be
considered both when selecting a site and when selecting ancillary
equipment for the site. Consider human, animal, and environmental
effects on the site.

Human impact

Often
the most secure sites are on private property, where people live.
Vandals and thefts are less likely to approach a station on private
land, where defacing the instrument would also be perceived as a crime
against the landowner.

Minimize
visibility of the instrumentation where possible. Build the station out
of sight of roadways, spray the monument and enclosure with
camouflaging paint, and install equipment low to the ground where
practical.

Use a locking enclosure where needed. Choose an enclosure that either has an internal lock or can be locked using a padlock.

Animal impact

Protect
against small animals (e.g. rodents) by sheathing external cables in
metal conduit. Consider burying cables where possible. This will also
protect against weathering.

Environmental impact

Use
a weatherproof enclosure for electronics, considering wind,
precipitation, and temperature. In hot regions, a fan or venting may be
necessary. In cold regions, use foam inserts to insulate the equipment.

Where needed, fix a radome over the GNSS antenna to protect from snow. This will also prevent birds from nesting on the antenna.